The crustaceans, especially krill, represent a vast resource as biological material. The amount of Antarctic krill (Euphausia superba), depending on the calculation method and investigation, is roughly 1 to 2×109 tons and the possible weight of the annual catch is estimated at 5 to 7×106 tons. These small crustaceans, which live in the cold waters around the Antarctic, are interesting as a source for proteins, lipids such as phospholipids, poly-unsaturated fatty acids etc., chitin/chitosan, astaxanthin and other carotenoids, enzymes and other materials.
Several methods for isolating above-mentioned materials have been developed. One problem is that the products may contain unwanted trace material included in the exoskeleton (also called integument or cuticle) of the crustaceans. For example, krill accumulates fluoride in their exoskeleton, thereby increasing the fluoride amount of any produced material either through the inclusion of parts of the exoskeleton or through extraction processes not taking into account the transfer of fluoride to the final material. In this case free fluoride or loosely bound fluoride may diffuse from the exoskeletal material and into the further processed material, making the end product high in fluoride ions and/or fluorinated compounds.
Fluoride is a compound that in high concentrations is detrimental for the health of land-dwelling animals as well as all kind of fish and crustaceans and especially fresh-water fish species, since fluoride atoms have the tendency of entering into the bone structure of such organisms and creating fluorosis, or weakening of the bone structure similar in its effect to osteoporosis, but different since it is the bone structure itself, and not the porosity of the bone that is affected. Skeletal fluorosis is a condition characterized by skeletal abnormalities and joint pain. It is caused by pathological bone formation due to the mitogenic action of fluoride on osteoblasts. In its more severe forms, skeletal fluorosis causes kyphosis, crippling and invalidism. Secondary neurological complications in the form of myelopathy, with or without radiculopathy, may also occur. High fluoride intake has also been shown to be toxic to the male reproductive system in rat experiments, and in humans high fluoride intake and symptoms of skeletal fluorosis have been associated with decreased serum testosterone levels. Consequently, if krill material is used as a starting material for food or feed products, precautions have to be taken for removing fluoride through the processing steps. However, the diffusion of fluoride and the presence of miniscule particles of the exoskeleton represent a problem that is difficult to overcome when processing krill material in an industrial scale.
Polar lipids such as phospholipids are essential for cell membranes and are also called membrane lipids. For most known animal species the content of polar lipids is nearly constant. However, this does not hold for the Antarctic krill. The phospholipids content varies from 2% up to 10% depending on the season. The high content, e.g. more than 5%, of the phospholipids is in principle good, but means also a problem, because it may result in strong emulsions in industrial processes. The emulsions complicate the separation of the lipid and proteinaceous fractions in the processes, such as hydrolysis.
The krill oil is one the valuable products made from krills. It contains inter glia phospholipids, triglycerides and carotenoid astaxanthin while being essentially free of protein, carbohydrates and minerals. Different portions of the krill material are separated from each other by, inter alia: i) crushing krill mechanically; ii) pressing them, iii) hydrolysis with heat and enzymes; iv) centrifugal force in rotating devices; and v) solvent extraction.
What is needed in the art are significant improvements to these rather conventional approaches and are described within many embodiments of the present invention (infra). For example, a disintegrated raw crustacean material may be separated and/or extracted into various enriched low-fluoride crustacean meal and/or oil compositions.